Method for separating ammonium sulfate from an aqueous solution of ammonium bisulfate and ammonium sulfate

ABSTRACT

A method is disclosed for separating ammonium sulfate from an aqueous solution of ammonium bisulfate and ammonium sulfate, and, in particular, where the aqueous solution additionally contains organics from a synthesis reaction. Separation is effected by the addition of an alcohol, preferably methanol, to the aqueous solution in an amount sufficient to precipitate substantially all of the ammonium sulfate and thereafter removing said precipitate from the solution.

United States Patent [1 1 Greco 1 51 Sept. 2, 1975 METHOD FOR SEPARATINGAMMONIUM SULFATE FROM AN AQUEOUS SOLUTION OF AMMONIUM BISULFATE ANDAMMONIUM SULFATE [75] Inventor. Nicholas P. (ireco, Pittsburgh. Pa.

[73] Assignee: Koppers Company. Inc.. Pittsburgh.

abandoned.

[52] U.S. Cl. 23/296; 23/300; 23/302 A; 423/520; 423/545 [51] Int. Cl.BOID 9/02; C01C 1/24 [58] Field of Search 23/296, 299. 300, 302, 23/302A; 423/517. 520. 545

[56] References Cited I UNITED STATES PATENTS 2.002.797 5/1935 Reich23/302 A 2.013.438 9/1935 Fitz 23/302 A 2.386.985 10/1945 Shaw 23/302 A2.666.687 l/l954 Skinner 23/300 3.366.681 l/1968 Thoma ct al 23/302 A3.408.157 10/1968 Miller ct alt 23/302 A 3.549.706 12/1972 Takaki ct al23/302 A 3.576.607 4/1971 Guttmann ct al 23/300 3.597.168 8/1971 Hoppcct a1. 23/302 A 3.709.666 1/1973 Westerveld ct a1 23/302 A FOREIGNPATENTS OR APPLICATIONS 205540 5/1956 Australia 23/302 A OTHERPUBLICATIONS Seidell. Solubility of lnorg. and Org. Cds.. Vol. 1. 1919.pages 63 to 66.

Primary E.\'uminrN0rman Yudkoff Assistant E.\'aminerS. J. EmeryAttorney, Agent. or Firm-Robert D. Yeager [57] ABSTRACT A method isdisclosed for separating ammonium sulfate from an aqueous solution ofammonium bisulfate and ammonium sulfate. and. in particular. where theaqueous solution additionally contains organics from a synthesisreaction. Separation is effected by the addition of an alcohol.preferably methanol. to the aqueous solution in an amount sufficient toprecipitate substantially all of the ammonium sulfate and thereafterremoving said precipitate from the solution.

4 Claims, N0 Drawings METHOD FOR SEPARA'IING AMMONIUM SULFATE FROM ANAQUEOUS SOLUTION ()F AMMONIUM BISULFATE AND AMMONIUM SULFATE This is acontinuation. of application Ser. No. 332,668. filed Feb. 15. l973 nowabandoned.

FIELD OF THE INVENTION The present invention relates to a method forseparating ammonium sulfate from ammonium bisulfate. and. in particular.to a method of separating ammonium sulfate from an aqueous solutioncontaining ammonium bisulfate and organic synthesis material.

BACKGROUND OF THE INVENTION It has recently been found that certainorganic synthesis can be carried out by utilizing ammonium bisulfate. Inmany of these reactions, ammonium sulfate is formed as a byproduct thatmust either be disposed of or regenerated. Because the disposal problemis now becoming inherently more difficult to deal with. it is highlydesirable to regenerate ammonium bisulfate therefrom. Not only doesregeneration effectively avoid or eliminate the disposal problem. italso renders the organic synthesis more economical.

Also, in many of the synthesis reactions. excess quantities of ammoniumbisulfate are preferred or required. In these reactions. not only isammonium sulfate a byproduct. but it is usually found with the excessquantities of ammonium bisulfate and certain unreacted or partiallyreacted organics utilized in the synthesis reaction. Various methods ofregeneration have recently been proposed. One such method first removesthe organics found in the aqueous solution of ammonium bisulfate andammonium sulfate to prevent undesirable foaming. Thereafter. a fusedmixture of ammonium bisulfate and ammonium sulfate is prepared which iscontacted with hot sweep gases to convert the ammonium sulfate tobisulfate.

While this method performs well and provides efficient regeneration ofammonium sulfate to bisulfate. it does require apparatus for handlinglarge quantities of ammonium bisulfate that does not need to beregenerated. Accordingly, it is desirable to have a method whichpreferentially separates the ammonium sulfate and organics from theaqueous solution containing them as well as ammonium bisulfate.

SUMMARY OF THE INVENTION The present invention provides a method forseparating ammonium sulfate from an aqueous solution containing same andammonium bisulfate. The method of the present invention also providesfor removing organics present in the aqueous solution of ammoniumbisulfate.

Generally, the method of the present invention comprises adding to anaqueous solution of ammonium bisulfate. ammonium sulfate, and residualorganics. if any. an alcohol. preferably methanol. The addition ofalcohol preferentially causes the precipitation of all of the ammoniumsulfate from the aqueous solution. Preferably. the ammonium sulfate isthereafter filtered and the filtered solids washed with an alcohol.preferably methanol. to clean any of the organics present thereon. Theorganics dissolved by the alcohol can be recovered after recovering thealcohol by distillation and recycled. if desired. back to the synthesisreaction together with the aqueous ammonium bisulfate solution. Be-

7 cause the method of the present invention provides for theprecipitation of substantially pure crystalline ammonium sulfate. thesulfate can be used substantially in precipitated or preferably washedform after drying of methanol as a fertilizer or may be regenerated toammonium bisulfate by known methods for use in the organic synthesis.

DESCRIPTION OF THE INVENTION Solutions of ammonium bisulfate. ammoniumsulfate and. optionally water. from organic synthesis reactions aretreated with alcohol. preferably methanol. after the synthesized producthas been removed therefrom. Suitable alcohols in addition to methanolinclude ethanol. butanol, isopropanol. and the like. However. because ofthe relative cheapness of methanol. it is preferred. The alcohol isadded to the aqueous solution preferably in amounts from about 400 to500% by weight of the amount of ammonium sulfate theoretically present.The temperature at which separation is effective to remove all of theammonium sulfate present is from pref erably to C.

It may be desirable to concentrate the aqueous solution prior to thesulfate removable. since less alcohol would be required to effectuateprecipitation. For instance. in Example 1 below. it was foundadvantageous to concentrate the raffinate by evaporation of of the waterpresent therein. This provided a more concentrated solution of ammoniumsulfate and ammonium bisulfate. With that particular concentration. for

example. substantially all of the ammonium sulfate present was removedby precipitation. That concentration of salt before precipitation isabout the minimum concentration possible while maintaining the salt insolution at room temperature.

The following generalized examples more clearly set forth the advantagesof the present invention:

EXAMPLE 1 EXAMPLE 2 Example 1 was repeated using methanol for theselective precipitation and recovery of ammonium sulfate from theconcentrated raffinate after extraction of the synthesized material. Theraffinate was thereafter fortified with ammonium bisulfate in water, anaromatic amine equal in amount to those consumed and recycled. Theresults of these runs are set forth in the following table:

TABLE Recovery of Ammonium Sulfate From Aqueous Mixtures With AmmoniumBisull'ate Resulting From S \nthetic Reactions Empltning Amines Products(Trude Reactor Charge. gv Product Synthesized g l Annlysig AromaticTemp.v Recovered ofTh -un "NC. ('yclc Amine NH,HS() (NH.). -S() hrs (1Yield Salt. 5 as l NHJ SO," (NHJ-SO NH,HS(),

I 32.4 158. 2 47 3 240 27.8 84.2 99.5 901) 9&0 2.0 I 27.3 NH) none 3 33025.0 )(H) 5L5 035 977 2.3 3 23.7 (ill: 27,7 .1 236 lit-1 73. $547 91.193.} I47 4 24.5 57.2 27.7 3 240 22.x v1.2 72.4 x10 9% (t4 5 none nonenone 2 240 2.] 8.4 Totals 1 12,9 -l-lh l 33. l I} 99.] 861 831 "lHN,);S(), obtained h difference after titration of NH,HS(),iConcentrated lU gnu 73 moles of water per theoretical mole of amine."Crude as analyletl [n he W 1" product. going Nlh'i corrected \ield."Assuming l m amine charged gi\ cs 2 m. (NH,

"'A\ g. reumcr mur four cycles What is claimed is:

l. A method for separating ammonium sulfate substantially free ofammonium bisulfate and organic impurities and obtaining a solution ofammonium bisulfate substantially free of any ammonium sulfate from anaqueous solution containing ammonium bisulfate and ammonium sulfate anddissolved organic impurities, said method consisting essentially ofconcentrating said solution to the maximum possible while maintainingthe salts in solution, adding to said aqueous solution an alcoholselected from the group consisting of methanol, ethanol, propanol,butanol, and isopropanol'in an amount of from about 400 to 500 percentby weight of the ammonium sulfate present in the solution and effectiveto precipitate substantially all of .said ammonium sulfate withoutprecipitating substantially any of the ammonium bisulfate and removingall of said precipitated ammonium sulfate from said solution to obtain asolution of ammonium bisulfate.

2. A method as set forth in claim 1 wherein said alcohol is methanol.

3. A method as set forth in claim 1 wherein said aqueous solution ismaintained between about and C.

4. A method for obtaining an aqueous solution of ammonium bisulfatesubstantially free of ammonium sulfate and any dissolved, and ammoniumsulfate substantially free of organic impurities from an aqueoussolution containing ammonium bisulfate, ammonium sulfate, and dissolvedorganic impurities, said method consisting essentially of concentratingsaid solution to the maximum possible while maintaining the salts insolution, adding to said'concentrated solution an alcohol selected fromthe group consisting of methanol, ethanol, propanol, butanol, andisopropanol, in an amount of from about 400 to 500 percent by weight ofthe ammonium sulfate present in the solution and effective toprecipitate substantially all of said ammonium sulfate substantiallyfree of ammonium bisulfate and organic impurities, removing saidprecipitated ammonium sulfate to form a remaining solution. andseparating said alcohol from said remaining solution to obtain saidaqueous solution of ammonium bisulfate.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION PATENT NO.3,902,859

DATED September 2, 1975 INVENTOR(S) 1 Nicholas P. Greco It is certifiedthat error appears in the above-identified patent and that said LettersPatent are hereby corrected as shown below:

[SEAL] Claim 4 should read as follows:

4. A method for obtaining an aqueous solution of ammonium bisulfatesubstantially free of ammonium sulfate, and ammonium sulfatesubstantially free of organic impurities from an aqueous solutioncontaining ammonium bisulfate, ammonium sulfate, and dissolved organicimpurities, said method consisting essentially of concentrating saidsolution to the maximum possible while maintaining the salts insolution, adding to said concentrated solution an alcohol selected fromthe group consisting of methanol, ethanol, propanol, butanol, andisopropanol, in an amount of from about 400 to 500 percent by weight ofthe ammonium sulfate present in the solution and effective toprecipitate substantially all of said ammonium sulfate substantiallyfree of ammonium bisulfate and organic impurities, removing saidprecipitated ammonium sulfate from solution to form a remainingsolution, and separating said alcohol from said remaining solution toobtain said aqueous solution of ammonium bisulfate.

Signed and Sealed this Attest:

RUTH C. MASON Arresting Officer C. MARSHALL DANN Commissioner of Pa tenrs and Trademarks

1. A METHOD FOR SEPARATING AMMONIUM SULFATE SUBSTANTIALLY FREE OFAMMONIUM BISULFATE AND ORGANIC IMPURITIES AND OBTAINING A SOLUTION OFAMMONIUM BISULFATE SUBSTANTIALLY FREE OF ANY AMMONIUM SULFATE FROM ANAQUEOUS SOLUTION CONTAINING AMMONIUM BISULFATE AND AMMONIUM SULFATE ANDDISSOLVED ORGANIC IMPURITIES, SAID METHOD CONSISTING ESSENTIALLY OFCONCENTRATING SAID SOLUTION TO THE MAXIMUM POSSIBLE WHILE MAINTAININGTHE SALTS IN SOLUTION, ADDING TO SAID AQUEOUS SOLUTION AN ALCOHOLSELECTED FROM THE GROUP CONSISTING OF METHANOL, ETHANOL, PROPANOL,BUTANOL, AND ISOPROPANOL IN AN AMOUNT OF FROM ABOUT 400 TO 500 PERCENTBY WEIGHT OF THE AMMINUM SULFATE PRESENT IN THE SOLUTION AND EFFECTIVETO PRECIPATE SUBSTANTIALLY ALL OF SAID AMMONIUM SULFATE WITHOUTPRECIPATING SUBSTANTIALLY ANY OF THE AMMONIUM BISULFATE AND REMOVING ALLOF SAID PRECIPITATED AMMONIUM SULFATE FROM SAID SOLUTION TO OBTAIN ASOLUTION OF AMMONIUM BISULFATE.
 2. A method as set forth in claim 1wherein said alcohol is methanol.
 3. A method as set forth in claim 1wherein said aqueous solution is maintained between about 15* and 30*C.4. A method for obtaining an aqueous solution of ammonium bisulfatesubstantially free of ammonium sulfate and any dissolved, and ammoniumsulfate substantially free of organic impurities from an aqueoussolution containing ammonium bisulfate, ammonium sulfate, and dissolvedorganic impurities, said method consisting essentially of concentratingsaid solution to the maximum possible while maintaining the salts insolution, adding to said concentrated solution an alcohol selected fromthe group consisting of methanol, ethanol, propanol, butanol, andisopropanol, in an amount of from about 400 to 500 percent by weight ofthe ammonium sulfate present in the solution and effective toprecipitate substantially all of said ammonium sulfate substantiallyfree of ammonium bisulfate and organic impurities, removing saidprecipitated ammonium sulfate to form a remaining solution, andseparating said alcohol from said remaining solution to obtain saidaqueous solution of ammonium bisulfate.